Vasovagal syncope: what to know

The autonomic nervous system normally adjusts circulation without conscious effort. In vasovagal syncope, a response to pain, fear, heat, prolonged standing, blood, coughing, or straining can slow the heart and widen blood vessels. Blood pressure falls, warning symptoms appear, and a person may briefly lose consciousness.

Common warnings include light-headedness, nausea, sweating, warmth, pale skin, blurred vision, or muffled hearing. Fainting itself is usually brief, but falls can cause injury. A similar presentation can occur with dehydration, anaemia, low blood sugar, medicines, or a heart rhythm problem, so context matters.

When warning symptoms begin, stop and lie down or sit somewhere safe. If lying down, raise your legs slightly if comfortable; use a side position when needed for comfort or pregnancy. Do not try to walk through the episode. After recovery, take fluids and food if appropriate, then stand slowly with support.

Reduce triggers by staying cool, avoiding long motionless periods, moving your calf muscles while standing, and keeping regular meals and fluids. Tell people close to you what warning signs you experience and ask them to protect you from hazards if you become unresponsive.

Emergency assessment is needed for fainting with chest pain, difficulty breathing, severe injury, persistent confusion, seizure-like activity, an unusual heartbeat, or collapse during exertion. Seek urgent help when there is no warning, recovery is slow, or breathing is abnormal.

Make a medical appointment after a first faint, repeated episodes, fainting while seated or lying down, or a change in your usual pattern. A clinician can review posture and triggers, examine you, check blood pressure and heart rhythm, and decide whether blood tests are needed.

Ask whether your episode sounds vasovagal, which warning signs require immediate action, and whether checks for anaemia, dehydration, hypoglycaemia, or an irregular rhythm would help explain it.